The present invention relates to a circulation fan apparatus having a circulation fan installed in a hermetic vessel containing a corrosive gas, and the invention also relates to a circulation-fan driving motor.
FIG. 8 shows an example construction of a conventional circulation fan apparatus, in which a circulation fan is installed in a hermetic vessel. In such a circulation fan apparatus, a corrosive process gas 3 necessary for various chemical processes and/or physical processes is enclosed in a hermetic vessel 1 at a predetermined pressure, and the process gas 3 is circulated by a circulation fan 2 in the hermetic vessel 1 to thereby perform predetermined processes.
A drive-side rotor 2-1 and a non-drive-side rotor 2-2 are fixed at both ends of a circulation fan 2, respectively. The drive-side rotor 2-1 is rotatably supported by a rotation bearing 31 supported by a drive-side bearing cover 30 and the non-drive-side rotor 2-2 is rotatably supported by a rotation bearing 41 supported by a non-drive-side bearing cover 40.
Furthermore, a driven magnet 32 is fixed to the drive-side rotor 2-1, and a driving magnet 33 is arranged outside of the hermetic vessel 1 in a position opposing the driven magnet 32, with the drive-side bearing cover 30 sandwiched therebetween. The driving magnet 33 is directly connected to a motor 34 to transfer a driving force to the drive-side rotor 2-1 of the circulation fan 2.
In the conventional apparatus stated above, the rotation bearing 31 and rotation bearing 41 are arranged in a hermetic space communicating with the hermetic vessel 1; therefore, lubricant used in the rotation bearings tends to contaminate the process gas. This causes a deterioration in the stability and reliability of processing, and necessitates relatively frequent replacement of the process gas. Furthermore, when the number of revolutions of the circulation fan 2 and bearing load are increased, the service life of the rotation bearings is shortened. Therefore, as the rotation bearings 31 and 41 are degraded, metal dust is generated and contaminates the process gas, contributing to a need to replace the process gas.
Furthermore, the motor 34 is disposed outside of the vessel, and a magnetic coupling formed of the driven magnet 32 and the driving magnet 33, which magnetically transfer a driving force, are used to transfer rotation force to the circulation fan 2. Therefore, when the number of revolutions is increased, the motor 34 and the magnets (the driven magnet 32 and the driving magnet 33) of larger sizes must be used, thus necessitating the use of a large installation space for the apparatus.
In consideration of the above problems, an object of the present invention is to provide a circulation fan apparatus and a circulation-fan driving motor, in which even when a circulation fan is rotated at high speed and under a high load, a process gas is not contaminated, alleviating the need for maintenance and allowing a smaller installation space to be employed.
Another object of the present invention is to provide a circulation fan apparatus and a circulation-fan driving motor, in which sections contacting with a process gas have anti-corrosion characteristics which thus exhibit a longer service life.
To solve the above problems, according to a first aspect of the present invention, a circulation fan apparatus including a hermetic vessel containing a corrosive process gas therein, and a circulation fan installed in said hermetic vessel, rotors of said circulation fan are rotatably supported by bearings, the apparatus is characterized in that the bearings comprise control-type radial magnetic bearings and at least one control-type axial magnetic bearing, displacement sensor targets and rotor-side magnetic poles of the radial magnetic bearings and axial magnetic bearing are fixed to the rotors of the circulation fan and are disposed in a hermetic space communicating with the hermetic vessel, and displacement sensors and stator-side magnetic poles opposing the displacement sensor targets and the rotor-side magnetic poles of the magnetic bearings are disposed outside of the hermetic vessel with cans or protection layers interposed therebetween.
As described above, the rotors of the circulation fan are rotatably supported by the control-type magnetic bearings, the displacement sensor targets and the rotor-side magnetic poles are disposed in the hermetic space communicating with the hermetic vessel, and the displacement sensors and the stator-side magnetic poles are disposed outside of the hermetic vessel with the cans or the protection layers interposed therebetween. In this case, the displacement sensors and the stator-side magnetic poles which tend to degrade the process gas do not contact with the process gas, so that it is possible to avoid the degradation of the process gas. Furthermore, the circulation fan in the hermetic vessel is supported by the magnetic bearings without being contacted, so that maintenance-free bearings can be realized.
Furthermore, according to a second aspect of the present invention, a circulation-fan driving motor for the abovementioned circulation fan apparatus is characterized in that a motor rotor is fixed to at least one rotor of the circulation fan, the motor rotor is disposed in the hermetic space communicating with the hermetic vessel, and a motor stator opposing the motor rotor is arranged outside of the hermetic vessel, with the can or the protection layer interposed therebetween.
As described above, the motor rotor that provides the circulation fan with a rotational driving force is fixed to the rotor of the circulation fan that is disposed in the hermetic space communicating with the hermetic vessel, and the stator is arranged outside of the hermetic vessel, with the can or the protection layer interposed therebetween. Thus, the stator that tends to degrade the process gas does not contact the process gas, so that it is possible to avoid the degradation of the process gas. Furthermore, since rotational driving force is provided to the circulation fan from the motor rotor, magnetic coupling is not required.
Furthermore, according to a third aspect of the present invention, the circulation fan apparatus described above is characterized in that either the displacement sensor targets of the control-type bearings or the rotor-side magnetic poles or both of them are formed of Permalloy (an iron-nickel alloy including 30 to 80% nickel).
Permalloy has anti-corrosion characteristics against the process gas. Therefore, as described above, by use of Permalloy to form either the displacement sensor targets of the control-type bearings or the rotor-side magnetic poles or both of them, anti-corrosion processing can be omitted for surfaces of the displacement sensor targets and the rotor-side magnetic poles. Accordingly, the distance between the rotor and stator can be reduced, by which performance and efficiency of magnetic bearings can be improved.
Furthermore, according to a fourth aspect of the present invention, the circulation fan apparatus or the circulation-fan driving motor described above is characterized in that the cans are formed of austenitic stainless steel.
Austenitic stainless steel has anti-corrosion characteristics against the process gas, has higher mechanical strength, and in addition, is nonmagnetic. Therefore, as described above, by using the austenitic stainless steel to form the cans, corrosion of the cans by the process gas can be avoided, thinner plates can be used for the cans, the distance between the individual rotors and stators of the magnetic bearings and the motor can be reduced, and in addition, magnetic force generated by the magnetic bearings and the motor will not be disrupted. Accordingly, longer service life, higher performance and efficiency, and smaller sizes can be realized for the circulation fan apparatus and the circulation-fan driving motor.
Furthermore, according to a fifth aspect of the present invention, the circulation fan apparatus or the circulation-fan driving motor described above is characterized in that the cans are formed of a nickel-molybdenum-chromium alloy.
The nickel-molybdenum-chromium alloy has anti-corrosion characteristics against the process gas, has higher mechanical strength, and in addition, is nonmagnetic. Therefore, as described above, by use of the nickel-molybdenum-chromium alloy to form the cans, corrosion of the cans by the process gas can be prevented, thinner plates can be used for the cans, the distance between the individual rotors and stators of the magnetic bearings and the motor can be reduced, and in addition, magnetic force generated by the magnetic bearings and the motor will not be disrupted. Accordingly, a longer service life, higher performance and efficiency, and smaller sizes can be realized for the circulation fan apparatus and the circulation-fan driving motor.
The aforementioned and other objects, characteristics, and advantages of the present invention will be more apparent by referring to a description below in conjunction with the accompanying drawings which show preferred embodiments of the present invention.